Generally, solar cell modules are made up of a rectangular solar cell panel and a frame member that holds the solar cell panel. Frame members having various types of structures for use in such solar cell modules are known.
As an example of a frame member structure, a frame member having a structure including an outer wall formed vertically along one side of a solar cell panel and a holding unit that is formed horizontally in an upper portion of the outer wall and that has a U-shaped cross section is known.
A solar cell module including the frame member employs a structure in which a solar cell panel is sandwiched by fitting a side of the solar cell panel into the holding unit having a U-shaped cross section of the frame member (see, for example, FIG. 2 of Patent Document 1).
In the solar cell module disclosed in Patent Document 1, the frame member includes, in addition to the solar cell panel sandwiching portion having a U-shaped cross section, an outer frame portion and an inner frame portion formed so as to extend downward from the solar cell panel sandwiching portion, and flange portions formed so as to be bent toward the inside at respective lower ends of the outer frame portion and the inner frame portion.
In the solar cell module structure disclosed in Patent Document 1, there is a space between the outer frame portion and the inner frame portion, but because an opening portion is present between the flange portion of the outer frame portion and the flange portion of the inner frame portion, the space is in communication with the exterior via the opening portion.
In this solar cell module, in order to attach the solar cell module onto a mounting base, a fitting is used that presses, from above, both the flange portion of the outer frame portion and the flange portion of the inner frame portion to attach the solar cell module onto the mounting base. In this case, this fitting is fixed to the mounting base with a bolt so as to attach the solar cell module onto the mounting base.
In the solar cell module having the above structure, as described above, in order to attach the solar cell module onto a mounting base, the fitting that presses the flange portion of the outer frame portion and the flange portion of the inner frame portion of the solar cell module is fixed to the mounting base. When an attempt is made to enhance the attachment strength of the solar cell module, it is necessary to increase the strength of the outer frame portion, the inner frame portion and the flange portions, that is to say, reinforcement is necessary such as increasing the thickness of these members.
However, the method of increasing the strength of the members by increasing the thickness of the members as described above can lead to increased size and weight of the solar cell module, and thus it cannot be said that this method is a beneficial countermeasure.
Under such circumstances, a method of increasing the strength of the members without using the above-described method of increasing the thickness of the members has been conceived and is generally in wide use. This method uses, for example, a frame member that is made up of an outer frame portion, an inner frame portion and a bottom portion, and that is internally provided with a hollow space portion. In a solar cell module using such a frame member that is internally provided with a hollow space portion, there is a space between the outer frame portion and the inner frame portion, but the space is closed by the bottom portion.
As used throughout this specification, in a solar cell module that holds the periphery of a solar cell panel using a frame member, the term “inside” means a “side on which the solar cell panel is present”, and the term “outside” means a side that is opposite to the “inside”, or in other words, a “side opposite to the side on which the solar cell panel is present”.